From a cohort of 4,047 obese patients (BMI ≥ 34 kg/m2 in men and ≥ 38 kg/m2 in women) with up to 15 years of follow-up, a group of 1,658 patients who had bariatric surgery were compared to 1,771 matched controls who did not have surgery. All patients were without diabetes at baseline. In the surgery group, 19% had banding, 69% had vertical banded gastroplasty, and 12% had gastric bypass. The controls received usual care, which ranged from no treatment to advanced lifestyle modification interventions. Matching was based on mean group characteristics for the entire SOS cohort using 18 demographic, anthropometric, and psychosocial variables. Significant baseline differences between the groups included higher BMI, blood pressure, total cholesterol, and daily caloric intake in the surgery group (p < 0.001 for each).